表大小-MariaDB Columnstore与InnoDB

我在MariaDB的ColumnStore上发现的每一项分析都声称它比InnoDB这样的常规引擎使用更少的磁盘空间，例如：

但这不是我在测试中发现的

CREATE TABLE `innodb_test` (id int, value1 bigint, value2 bigint, value3 bigint, value4 bigint, value5 bigint) ENGINE=innodb;

CREATE TABLE `columnstore_test` (id int COMMENT 'compression=2', value1 bigint COMMENT 'compression=2', value2 bigint COMMENT 'compression=2', value3 bigint COMMENT 'compression=2', value4 bigint COMMENT 'compression=2',value5 bigint COMMENT 'compression=2') ENGINE=columnstore;

在表中插入值为0的100万行（5列）：

INSERT INTO innodb_test
SELECT CONCAT(a1.id,a2.id,a3.id,a4.id,a5.id,a6.id),
0,0,0,0,0
from 
  (select 0 as id union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) a1, 
  (select 0 as id union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) a2,
  (select 0 as id union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) a3,
  (select 0 as id union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) a4,
  (select 0 as id union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) a5,
  (select 0 as id union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) a6;

INSERT INTO columnstore_test SELECT * FROM innodb_test;

columnstore表的大小大于innoDB表：

call columnstore_info.table_usage(NULL, 'columnstore_test');
+--------------+------------------+-----------------+-----------------+-------------+
| TABLE_SCHEMA | TABLE_NAME       | DATA_DISK_USAGE | DICT_DISK_USAGE | TOTAL_USAGE |
+--------------+------------------+-----------------+-----------------+-------------+
| size_comp    | columnstore_test | 352.05 MB       | 0 Bytes         | 0 Bytes     |
+--------------+------------------+-----------------+-----------------+-------------+

SELECT table_name, (data_length + index_length) / (1024 * 1024) "Size in MB"  FROM information_schema.tables WHERE table_schema = schema() AND table_name = 'innodb_test';
+-------------+------------+
| table_name  | Size in MB |
+-------------+------------+
| innodb_test | 71.6094    |
+-------------+------------+

此外，如果我在不压缩的情况下创建表，则大小相同：

CREATE TABLE `columnstore_no_compression` (id int COMMENT 'compression=0', value1 bigint COMMENT 'compression=0', value2 bigint COMMENT 'compression=0', value3 bigint COMMENT 'compression=0', value4 bigint COMMENT 'compression=0',value5 bigint COMMENT 'compression=0') ENGINE=columnstore;

INSERT INTO columnstore_no_compression SELECT * FROM innodb_test;

call columnstore_info.table_usage(NULL, 'columnstore_no_compression');
+--------------+----------------------------+-----------------+-----------------+-------------+
| TABLE_SCHEMA | TABLE_NAME                 | DATA_DISK_USAGE | DICT_DISK_USAGE | TOTAL_USAGE |
+--------------+----------------------------+-----------------+-----------------+-------------+
| size_comp    | columnstore_no_compression | 352.00 MB       | 0 Bytes         | 0 Bytes     |
+--------------+----------------------------+-----------------+-----------------+-------------+

我正在使用mariadb-columnstore-1.1.2-1版本

my.ini文件：

[client]
port = 3306
socket          = /usr/local/mariadb/columnstore/mysql/lib/mysql/mysql.sock

[mysqld]
loose-server_audit_syslog_info = columnstore-1
port = 3306
socket          = /usr/local/mariadb/columnstore/mysql/lib/mysql/mysql.sock
datadir         = /ssd/mariadb/db
skip-external-locking
key_buffer_size = 512M
max_allowed_packet = 1M
table_cache = 512
sort_buffer_size = 4M
read_buffer_size = 4M
read_rnd_buffer_size = 16M
myisam_sort_buffer_size = 64M
thread_cache_size = 8
query_cache_size = 0
thread_stack = 512K
lower_case_table_names=1
group_concat_max_len=512
sql_mode="ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"
infinidb_compression_type=2
infinidb_stringtable_threshold=20
infinidb_local_query=0
infinidb_diskjoin_smallsidelimit=0
infinidb_diskjoin_largesidelimit=0
infinidb_diskjoin_bucketsize=100
infinidb_um_mem_limit=0
infinidb_use_import_for_batchinsert=1
infinidb_import_for_batchinsert_delimiter=7
basedir                         = /usr/local/mariadb/columnstore/mysql/
character-sets-dir              = /usr/local/mariadb/columnstore/mysql/share/charsets/
lc-messages-dir                 = /usr/local/mariadb/columnstore/mysql/share/
plugin_dir                      = /usr/local/mariadb/columnstore/mysql/lib/plugin
binlog_format=ROW
server-id = 1
log-bin=/usr/local/mariadb/columnstore/mysql/db/mysql-bin
relay-log=/usr/local/mariadb/columnstore/mysql/db/relay-bin
relay-log-index = /usr/local/mariadb/columnstore/mysql/db/relay-bin.index
relay-log-info-file = /usr/local/mariadb/columnstore/mysql/db/relay-bin.info
tmpdir          = /ssd/tmp/

[mysqldump]
quick
max_allowed_packet = 16M

[mysql]
no-auto-rehash

[isamchk]
key_buffer_size = 256M
sort_buffer_size = 256M
read_buffer = 2M
write_buffer = 2M

[myisamchk]
key_buffer_size = 256M
sort_buffer_size = 256M
read_buffer = 2M
write_buffer = 2M

[mysqlhotcopy]
interactive-timeout

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这是预期的行为还是我做错了什么？

我是MariaDB ColumnStore的首席软件工程师

ColumnStore针对大型数据集进行了优化，并为列预先分配了磁盘空间。这样做的好处是，在磁盘轴上，碎片的可能性较小。缺点是在像您这样的小型数据集上，会分配大量未使用的空间

它首先为第一列数据块预分配256KB，然后将其扩展到2^23行（刚好超过800万行）。因此，对于每个BIGINT列，它将预分配64MB，对于INT，它将预分配32MB。压缩文件上的头块的压缩/未压缩之间的小差异。我们有一些信息\u架构表，可以显示实际使用情况（在8KB以内）：

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因此，除非您计划使用更大的数据集（至少在几GB范围内），否则很遗憾，当数据很少时，您将看到大量磁盘使用。

对不起，我没有注意到您已经找到了I_S表。table/total usage过程中存在一个已知错误，当没有数据字典时，该错误会产生一个0字节的结果。这将在1.1.4中固定。